Spine stabilization system with self-cutting rod

ABSTRACT

A spine stabilization system is provided. The system utilizes a self-cutting rod having a sharp cutting edge that can be anchored to a patient&#39;s spine with pedicle screws. The system can be percutaneously delivered, low profile, and allow cutting of surrounding tissue rather than simply spreading the tissue apart during rod insertion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/478,596 filed April 25, 2011, and entitled “Spine StabilizationSystem with Self-Cutting Rod,” the contents of which are incorporatedherein by reference in their entirety.

FIELD

The present invention relates to spine stabilization systems having arod for spine stabilization that is anchored with fixation screws, andmore particularly to a spine stabilization system utilizing aself-cutting rod that can be fixed to a patient's spine with pediclescrews.

BACKGROUND

Spinal correction surgery is used to correct spine deformities,disorders, or diseases, and otherwise stabilize the spine. Spinalcorrection surgery is sometimes needed to relieve pain or correct thealignment of a patient's spine. For example, spinal correction surgeryis often used to treat spinal diseases, such as scoliosis andosteoarthritis, as well as degenerative disc diseases.

Pedicle screws are an integral part of most spinal correction surgeries.For example, a common surgery involves an internal fixation of thedamaged or diseased vertebrae using a pedicle screw implant with a fixedlink to a plate or a rod. A critical diameter for spinal surgery is thusthe inner diameter of the pedicle of the vertebral body being treated.The inner diameter, however, can vary widely because it is directlyrelated a person's height and the anatomy of each individual's cervicalspine, thoracic and lumbar spine, and sacrum. Therefore, for asuccessful spinal surgery, the surgeon must be able to understand eachpatient's anatomical differences.

In most rod fixation systems, the pedicle screws are attached to a rodreceiving head that is typically shaped like a tulip head for connectingto the rod. Although most systems provide a screw and rod receiving headcombination that can articulate relative to one another, so that thetulip heads can align after the screws are inserted into the bone, it isnevertheless still difficult and time consuming to properly align arigid rod into a pair of tulip heads. Compounding this problem is thesurrounding tissue around the insertion area, which can be extremelytough to circumvent. The surgeon often has to exert a significant amountof force to spread apart the native tissue in order to properly seat therod inside the tulip heads, thereby creating even more trauma to theinjury site. With the additional challenges previously mentioned withproper pedicle screw insertion, there is a need for a better, moreefficient rod fixation system for the spine.

Accordingly, it is desirable to provide a spinal fixation system thatutilizes known techniques of rod stabilization with pedicle screws, buthaving the new feature of a self-cutting rod that has a cutting edge toquickly and easily insert in between the pedicle screws duringimplantation.

SUMMARY

The present disclosure provides a spine stabilization system utilizing aself-cutting rod that can be fixed to a patient's spine with pediclescrews. The system can be percutaneously delivered, low profile, andallow cutting of surrounding tissue rather than simply spreading thetissue apart during rod insertion.

In one embodiment, a spine stabilization system is provided. The spinestabilization system comprises fixation screws for anchorage to bonetissue. Each screw may comprise a shaft portion attached to a headportion at an articulating joint. The head portion may be configured tohold a rod therein. The system may also comprise a bushing having asaddle region or slot for receiving a rod, the bushing being configuredto nest within the head portion. A rod having a cutting edgesufficiently sharp to tear through fascia and muscle tissue is alsoprovided.

In another embodiment, a method for stabilizing a spine is provided. Themethod comprises providing a system having fixation screws for anchorageto bone tissue, each screw comprising a shaft portion attached to a headportion at an articulating joint, the head portion configured to hold arod therein. The system may also comprise a bushing having a saddleregion or slot for receiving a rod, the bushing being configured to nestwithin the head portion. A rod having a cutting edge sufficiently sharpto tear through fascia and muscle tissue is also provided. The methodfurther includes the steps of inserting the fixation screws into bonetissue, and inserting the rod into the head portions of the fixationscrews, wherein the step of inserting the rod comprises pressing thecutting edge of the rod through fascia and muscle tissue until thecutting edge of the rod is seated within the saddle region of thebushing.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosure. Additional features of thedisclosure will be set forth in part in the description which follows ormay be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 is a side view of an exemplary embodiment of a rod fixationsystem of the present disclosure.

FIG. 2 is a top-down view of the rod fixation system of FIG. 1.

FIG. 3 is a perspective view of the rod fixation system of FIG. 1.

FIG. 4A is a cross-sectional view of the rod fixation system of FIG. 1along lines A-A.

FIG. 4B is an enlarged view of the encircled portion of the rod fixationsystem of FIG. 4A.

FIG. 5 is a partial cutaway end view of the rod fixation system of FIG.1.

FIG. 6 is an end view of another exemplary embodiment of a rod of thepresent disclosure.

FIG. 7 is an end view of still another exemplary embodiment of a rod ofthe present disclosure.

FIG. 8A is a perspective view of yet another exemplary embodiment of arod of the present disclosure.

FIG. 8B is a perspective view of event still another exemplaryembodiment of a rod of the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

The present disclosure provides a spine stabilization system utilizing aself-cutting rod that can be fixed to a patient's spine with pediclescrews, such as polyaxial screws. The system is configured as a rodfixation system that can be percutaneously delivered, low profile, andallow cutting through the surrounding tissue rather than simplyspreading the tissue apart during rod insertion.

In FIG. 1, an exemplary embodiment of a spine stabilization system 10 ofthe present disclosure is shown. The spine stabilization system 10 mayinclude a rod 20 for rigid fixation of a weakened, diseased or damagedvertebral segment of a patient's spine. The rod 20 may be anchored tothe patient's spine with fixation elements such as pedicle screws 30.Pedicle screws 30 may be polyaxial for greater flexibility. Pediclescrews 30 may have a threaded shaft 32. In the embodiment shown, thethreaded shaft 32 may be dual threaded, if so desired. The threadedshaft 32 may extend into a neck 34 that terminates into a rounded end orball 36. A tool-engaging opening 38 may be provided on the ball 36 toallow the screw 30 to engage with insertion tools or drivers. Forexample, the opening 38 may be polygon-shaped (as shown in FIGS. 4A and4B) such as for example, a hexagon-shaped opening.

Referring now to FIG. 3, the ball 36 may be configured to cooperate witha head portion 40 of the screw 30. The head portion may be a generallytulip-shaped head. The head portion 40, or rod holder, of the screw 30may have a hollow core 44 or opening, and a tapered end 42 at which theball 36 of the screw 30 may rest. The ball 36 of the screw 30 and thetapered end 42 of the head portion 40 form a ball-and-socket type jointthat allows some articulation of the head portion 40 relative to theshaft portion 32 of the screw 30. Within the hollow core 44 of the headportion 40 may be a bushing 50 that provides a slot or an open, saddleregion 52 to hold and secure the rod 20 inside the head portion 40. Thebushing 50 may be configured to nest within the head portion 40 andagainst the ball 36 of the screw 30, as shown in FIGS. 4A and 4B. Thehead portion 40 may also be provided with a flange 48 that encircles theexterior. This flange 48 may facilitate locating the head portion 40during surgery by providing a visual cue, as well as serve as aconvenient grip for handling the head portion 40.

As shown in FIG. 2, locking caps 60 may be provided to secure the rod 20inside the head portion 40 and close off the hollow core 44. The lockingcaps 60 may comprise a tool bore 62 for receiving an insertion tool. Thelocking caps 62 may further comprise a threaded exterior 64 for threadedengagement with the head portion 40, as illustrated in detail in FIG.4B. Of course, it is understood that threads are merely one example ofan attachment mechanism. Other mechanisms may be equally employed, suchas a snap-fit or press-fit arrangement between the locking cap 60 andthe head portion 40.

The rod 20 of the present disclosure may include a cutting edge 22sufficiently sharp enough to cut easily through surrounding tissues ofthe spine. The rod 20, in effect, is a cutting blade. And while the term“rod” generally refers to a cylindrical shaped object, as shown in FIGS.3, 4A and 4B the rod 20 of the present embodiment may beteardrop-shaped, terminating at one end into its cutting edge 22. It iscontemplated that the rod 20 may be suitable for transfacial andtransmuscular insertion into the head portions 40 simply by exertingforce onto the rod 20, whereby the cutting edge 22 will cut through thefascia and muscle easily and quickly. Unlike with conventional rods, therods 20 of the present disclosure do not merely spread apart thesurrounding tissue, but cut entirely through them when the rods 20 arelodged into place. It is believed that the clean, smooth cutting of thesurrounding tissue in this manner not only saves a great deal of timeduring surgery, but also provides the additional benefit of disruptingless of the patient's natural tissue than with conventional spreadingtechniques. This localized cutting effect results in less painpost-surgery, and a faster and more complete healing of the surroundingtissue (i.e., compared to the healing time of a deep, clean cut versus ajagged edged, inconsistent cut).

In use, a surgeon would first implant the head portions 40, bushings 50and pedicle screws 30 into the pedicles of the vertebrae to be rigidlyfixed. As is commonly known in the art, the head portions 40, bushings50 and pedicle screws 30 may be provided pre-assembled for convenience.After proper insertion of the pedicle screws 30, the surgeon may simplypush down (by hand or with the assistance of a tool) on the rod 20 toseat the rod 20 inside the saddle region 52 of each of the two bushings50 within the head portions 40. The cutting edge 22 of the rod 20 may besufficiently sharp enough to cut through surrounding fascia and musclewithout significant resistance, thereby allowing easy and fastinsertion. When the self-cutting rod 20 has been properly seated, thelocking caps 60 may be placed over the head portions 40 and the entiresystem 10 can be closed up. Due to the ability of the rod 20 to seat soclosely to the ball 36 of the screw 30, the spine stabilization system10 of the present disclosure offers a very low profile. Further, theentire system 10 may be percutaneously delivered.

In order to avoid any unintended and unnecessary tearing, scraping ordamage to the tissues near the ends of the rod 20, the head portions 40may be configured with a close-off end, as contemplated in the end viewat FIG. 5 whereby a portion of the head portion 40 is removed to showthe rod 20 inside the head portion 40. In other words, the head portion40 itself (or in cooperation with the bushing 50 as a unit) forms aclosed end that prevents the cutting edge 22 of the rod 20 fromcontacting adjacent tissue.

It is contemplated that the rod 20 may be formed of any suitable medicalgrade metal, such as titanium, titanium alloy, stainless steel, orcobalt chrome. The rod 20 may also be formed from a variety of othersuitable biocompatible materials, either alone or in combination withone another, so long as the material provides enough rigidity for therod 20 to serve as a spinal fixation implant. The rod 20 may be ABSinjection molded plastic, polyetheretherketone (PEEK), polyethylene(PE), or ultra high molecular weight polyethylene (UHMWPE). If desired,the devices may be bioabsorbable or bioresorbable. In other embodiments,the rod 20 may be formed partially or wholly from a radiolucentmaterial. For example, the rod 20 may be formed from a material blendedwith a radiopaque material, such as barium sulfate, to assist in thevisualization of the rod 20 insertion process. In addition, radiopaquemarkers may be employed with the rod 20 as well as the head portion 40for imaging possibilities. Additionally, the rod 20 may contain acoating having biological properties, such as with antibiotic,antimicrobial, blood coagulating, or bone growth promoting properties,as some examples. Other known biologically active agents may also beemployed, as desired.

As previously mentioned, it is possible to combine rigid materials withother semi-rigid materials to form a composite rod 20. For instance, inone embodiment, the rod 20 may include a top side (i.e., rounded side)that is relatively softer than the cutting edge 22 (i.e., blade side).In addition, a soft coating may be applied to the top side for ease ofhandling, if so desired.

The cutting edge 22 may be integrally formed from rod 20. Alternatively,the cutting edge 22 may be a separate component that is attached to therod 20 either permanently or semi-permanently. For example, the cuttingedge 22 may be glued or mechanically attached to the rod 20 usingscrews, a press fit, an interference fit, and the like. The cutting edge22 may thus be constructed from the same or different material as therod 20. This allows for customization of the cutting edge 22, forexample to provide a desired sharpness, width, and the like. The cuttingedge 22 may also be formed from a variety of other suitablebiocompatible materials, either alone or in combination with oneanother, so long as the material provides enough rigidity to serve as acutting edge. The cutting edge 22 may be ABS injection molded plastic,PEEK, PE, or UHMWPE. If desired, some or all of the cutting edge 22 maybe bioabsorbable or bioresorbable.

In other embodiments, the cutting edge may be formed partially or whollyfrom a radiolucent material. Additionally, the cutting edge 22 maycontain a coating having biological properties, such as with antibiotic,antimicrobial, blood coagulating, or bone growth promoting properties,as some examples. Other known biologically active agents may also beemployed, as desired. While the rod 20 of the present embodiment isshown as having a V-shaped cutting edge 22 from a side view, it isunderstood that other shapes may be employed, such as a W-shaped cuttingedge, as shown in FIG. 6. Other shapes may also include waves, or jaggededges, serrations, or the like. In addition, it is possible to have acomposite rod 20 comprising a rod-like portion A that attaches to acutting-edge portion B, as shown in FIG. 7, for ease of manufacture. Inone embodiment, the rod 20 (along with its cutting edge 22) may have atotal diameter in the range of about 6.0 mm.

FIGS. 8A and 8B illustrate other embodiments of a cutting rod of thepresent disclosure. In FIG. 8A, the rod 120 shares similar features tothe rod 20 previously described, with like elements sharing the samereference numeral following the prefix “1”, while in FIG. 8B, the rod220 shares similar features to the rod 20 previously described, withlike elements sharing the same reference numeral following the prefix“2”. Rods 120, 220 may have intermittent cutting edges, or adiscontinuous cutting edge when viewed as a whole. For example, rod 120may be provided with a plurality of cutting edges 122, with non-cuttingportions 124 separating the cutting edges 122 from each other. Likewise,rod 220 may also include a plurality of cutting edges 222, each cuttingedge 222 being separated from the next by spaces or portions 224 thatmay not be specifically configured to cut through tissue. Of course, thecutting edges of the rods 120, 220 should be suitable for transfacialand transmuscular insertion into the screws 30 and configured to cutthrough the fascia and muscle easily and quickly, similar to the cuttingedge 22 of rod 20.

The description of the invention is provided to enable any personskilled in the art to practice the various embodiments described herein.While the present invention has been particularly described withreference to the various figures and embodiments, it should beunderstood that these are for illustration purposes only and should notbe taken as limiting the scope of the invention.

There may be many other ways to implement the invention. Variousfunctions and elements described herein may be partitioned differentlyfrom those shown without departing from the spirit and scope of theinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and generic principles definedherein may be applied to other embodiments. Thus, many changes andmodifications may be made to the invention, by one having ordinary skillin the art, without departing from the spirit and scope of theinvention.

A reference to an element in the singular is not intended to mean “oneand only one” unless specifically stated, but rather “one or more.” Theterm “some” refers to one or more. Underlined and/or italicized headingsand subheadings are used for convenience only, do not limit theinvention, and are not referred to in connection with the interpretationof the description of the invention. All structural and functionalequivalents to the elements of the various embodiments of the inventiondescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and intended to be encompassed by the invention.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe above description.

1. A spine stabilization system comprising: fixation screws foranchorage to bone tissue, each screw comprising a shaft portion attachedto a head portion at an articulating joint, the head portion configuredto hold a rod therein; a bushing having a saddle region for receiving arod, the bushing being configured to nest within the head portion; and arod including a cutting edge sufficiently sharp to tear through fasciaand muscle tissue.
 2. The system of claim 1, wherein the rod has aV-shaped cutting edge.
 3. The system of claim 1, wherein the rod has aW-shaped cutting edge.
 4. The system of claim 1, wherein the rodincludes one or more cutting edges.
 5. The system of claim 1, whereinthe cutting edge is discontinuous.
 6. The system of claim 1, wherein thecutting edge is attachable to the rod.
 7. The system of claim 1, furtherincluding a locking cap for engagement with the head portion.
 8. Thesystem of claim 1, wherein the articulating joint is a ball-and-sockettype joint.
 9. A method for stabilizing a spine comprising: providing aspine stabilization system having fixation screws for anchorage to bonetissue, each screw comprising a shaft portion attached to a head portionat an articulating joint, the head portion configured to hold a rodtherein, a bushing having a saddle region for receiving a rod, thebushing being configured to nest within the head portion, and a rodhaving a cutting edge sufficiently sharp to tear through fascia andmuscle tissue; inserting the fixation screws into bone tissue; andinserting the rod into the head portions of the fixation screws; whereinthe step of inserting the rod comprises pressing the cutting edge of therod through fascia and muscle tissue until the cutting edge of the rodis seated within the saddle region of the bushing.
 10. The method ofclaim 9, wherein the fixation screws are pedicle screws, and the bonetissue are pedicles.
 11. The method of claim 9, further including thestep of placing locking caps over the head portions.
 12. The method ofclaim 9, wherein the system is assembled percutaneously.